THỦY SẢN CHÍNH SẢN XUẤT Suất cơ bản trong các hệ thống thuỷ sản, giống như quá trình tương tự trong các môi trường trên cạn, cung cấp các cơ sở của mạng lưới thức ăn mà tất cả các cấp cao hơn của một hệ sinh thái phụ thuộc. Năng suất sinh học là sự gia tăng trong vật liệu hữu cơ trên một đơn vị diện tích, khối lượng với thời gian. Bổ sung các chất hữu cơ này là vật chất mà từ đó các cộng đồng thực vật và động vật khác nhau của một hệ sinh. | AQUATIC PRIMARY PRODUCTION Primary productivity in aquatic systems like the same process in terrestrial environments provides the base of the food web upon which all higher levels of an ecosystem depend. Biological productivity is the increase in organic material per unit of area or volume with time. This addition of organic matter is the material from which the various plant and animal communities of an ecosystem are made and is dependent on the conversion of inorganic matter into organic matter. Conversion is accomplished by plants through the photosynthetic process. Plants are therefore considered to be the primary producers and in an aquatic ecosystem these plants include algae bacteria and sometimes higher plants such as water grasses and water lillies. Primary productivity the first level of productivity in a system can be measured as the rate of photosynthesis addition of biomass per unit of time yield or indirectly by nutrient loss or a measure of respiration of the aquatic community. METHODS OF STUDY Standing crop refers to the part of biological production per unit area or per unit volume that is physically present as biomass and that is not lost in respiration. Standing crop measurements over a period of time give an indirect measure of productivity in terms of yield. Plankton microscopic floating plants and animals can be collected in a plankton net and may be counted under a microscope or weighed. Aquatic biologists have used standing crop measurements to estimate productivity longer than any other method . Lohman 1908 . This method is still also used for periphyton attached algae or rooted plants. Only within the past few decades have biologists progressed from merely counting numbers of organisms to calculating biomass and more recently to expressing biomass yield. Fishery biologists like farmers for many years have measured fish productivity in terms of tons produced per acre of water surface per year. Calculating biomass and biomass yield is an
